A requirement of most electronic systems is a regulated source of direct current (DC) voltage. Whether the DC power originates with a battery or has been converted from alternating current (AC) power, a voltage regulator circuit is usually required to provide a steady DC voltage.
FIG. 1 illustrates a simple power supply circuit 100 that includes a voltage regulator. In power supply circuit 100, the voltage provided by AC voltage source 110 is increased or decreased by transformer 112 to a voltage having a magnitude that is required by the load. The transformed voltage passes through rectifier 114, which is a set of diodes in FIG. 1. The voltage is then filtered by capacitive filter 116. The resulting voltage is regulated by voltage regulator 118, which can be a discrete component circuit or an integrated circuit voltage regulator. Either way, the output voltage is filtered through inductive filter 120. The filtered voltage is then supplied to load 122, which could be, for example, an integrated circuit such as a microprocessor.
To supply voltage to an integrated circuit, transformer 112, rectifier 114, capacitive filter 116, and voltage regulator 118 are typically consolidated into a voltage regulator module (VRM), which is a discrete component that is mounted on a printed circuit (PC) board. Inductive filter 120 typically is a separate component, due to the relatively large size of the inductor.
FIG. 2 illustrates a VRM 202 and an inductive filter 204 located on a PC board 206 of a computer system in accordance with the prior art. To supply power to an integrated circuit, electrical current first travels from the VRM 202 through the inductive filter 204. The current then travels through traces (not shown) in PC board 206, and up through socket 208 to pins 210 of an integrated circuit (IC) package 212 The current continues along traces (not shown) in IC package 212 to connections 214. Connections 214 make electrical contact with pads (not shown) on the integrated circuit 216.
The scale and/or location of pins 210 on an IC package 212 may be different from the scale and/or location of pin holes on the socket 208. Thus, in some systems, an interposer (not shown) exists between the IC package 212 and the socket 208. The interposer essentially is a small printed circuit board that provides a dimensional interface between the IC package pins 210 and the pin holes of the socket 208. When an interposer is present, the supplied current must also travel through the interposer to reach the integrated circuit.
A voltage drop occurs between VRM 202 and integrated circuit 216, due to losses along the path between VRM 202 and integrated circuit 216. All other things being equal, the farther the distance between VRM 202 and integrated circuit 216, the larger the voltage drop. At relatively low voltages, this voltage drop is a tolerable effect that is compensated for by providing a VRM that supplies a higher voltage than is actually needed by the integrated circuit. A negative side effect of this strategy, however, is that the VRM may need to be larger than necessary, and power is inefficiently consumed.
Technological advancements in integrated circuit technologies are driving frequency requirements higher, and driving voltages and voltage margins lower. Therefore, it is desirable to reduce the inefficient power consumption caused by the voltage drop between the VRM and the integrated circuit. This reduction in voltage drop can be achieved by moving the VRM and inductive filter as close as possible to the integrated circuit. However, the proximity of the VRM and inductive filter to the integrated circuit is limited by the fact that the VRM and inductive filter must be located on the PC board in prior art systems.
For the reasons stated above and for other reasons stated below, which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a circuit configuration enabling a VRM and inductive filter to be placed closer to the integrated circuit than is possible in prior art systems.